During the forthcoming grant period we propose to: (1) analyze the structure and connections of the primate hippocampal formation; (2) determine the capacity of this system to reorganize itself after the selective removal of certain afferent pathways; and (3) continue our studies of the morphological and functional properties of isolated hippocampal neurons grown in dispersed culture. Current knowledge of the organization of the hippocampal formation is derived almost entirely from the study of the common laboratory rodents (especially rats and mice), and while it is widely assumed that the view of the hippocampus that has emerged from these studies is applicable to primates (including man), it remains to be shown that the same pattern of connectivity exists in the primate brain and that primates display the same capacity for morphological plasticity. The demonstration that fetal hippocampal neurons survive well in dispersed culture and frequently express their characteristic phenotype in vitro makes them particularly suitable for biochemical, electrophysiological and pharmacological study. While continuing the analysis of the surface of these cells and their ability to synapse with each other, we hope to begin to analyze their functional properties and their response to iontophoretically applied known and putative neurotransmitters.